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authorWill Deacon <will@kernel.org>2019-11-21 11:58:58 +0000
committerIngo Molnar <mingo@kernel.org>2019-11-25 09:15:21 +0100
commit1eb085d94256aaa69b00cf5a86e3c5f5bb2bc460 (patch)
tree33510b14c7d093cbedf09d156e8dc6899004846d /include
parentdcb786493f3e48da3272b710028d42ec608cfda1 (diff)
downloadlinux-1eb085d94256aaa69b00cf5a86e3c5f5bb2bc460.tar.bz2
locking/refcount: Move saturation warnings out of line
Having the refcount saturation and warnings inline bloats the text, despite the fact that these paths should never be executed in normal operation. Move the refcount saturation and warnings out of line to reduce the image size when refcount_t checking is enabled. Relative to an x86_64 defconfig, the sizes reported by bloat-o-meter are: # defconfig+REFCOUNT_FULL, inline saturation (i.e. before this patch) Total: Before=14762076, After=14915442, chg +1.04% # defconfig+REFCOUNT_FULL, out-of-line saturation (i.e. after this patch) Total: Before=14762076, After=14835497, chg +0.50% A side-effect of this change is that we now only get one warning per refcount saturation type, rather than one per problematic call-site. Signed-off-by: Will Deacon <will@kernel.org> Reviewed-by: Ard Biesheuvel <ardb@kernel.org> Reviewed-by: Kees Cook <keescook@chromium.org> Tested-by: Hanjun Guo <guohanjun@huawei.com> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org> Cc: Elena Reshetova <elena.reshetova@intel.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: https://lkml.kernel.org/r/20191121115902.2551-7-will@kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'include')
-rw-r--r--include/linux/refcount.h39
1 files changed, 20 insertions, 19 deletions
diff --git a/include/linux/refcount.h b/include/linux/refcount.h
index e3b218d669ce..1cd0a876a789 100644
--- a/include/linux/refcount.h
+++ b/include/linux/refcount.h
@@ -23,6 +23,16 @@ typedef struct refcount_struct {
#define REFCOUNT_INIT(n) { .refs = ATOMIC_INIT(n), }
+enum refcount_saturation_type {
+ REFCOUNT_ADD_NOT_ZERO_OVF,
+ REFCOUNT_ADD_OVF,
+ REFCOUNT_ADD_UAF,
+ REFCOUNT_SUB_UAF,
+ REFCOUNT_DEC_LEAK,
+};
+
+void refcount_warn_saturate(refcount_t *r, enum refcount_saturation_type t);
+
/**
* refcount_set - set a refcount's value
* @r: the refcount
@@ -154,10 +164,8 @@ static inline __must_check bool refcount_add_not_zero(int i, refcount_t *r)
break;
} while (!atomic_try_cmpxchg_relaxed(&r->refs, &old, old + i));
- if (unlikely(old < 0 || old + i < 0)) {
- refcount_set(r, REFCOUNT_SATURATED);
- WARN_ONCE(1, "refcount_t: saturated; leaking memory.\n");
- }
+ if (unlikely(old < 0 || old + i < 0))
+ refcount_warn_saturate(r, REFCOUNT_ADD_NOT_ZERO_OVF);
return old;
}
@@ -182,11 +190,10 @@ static inline void refcount_add(int i, refcount_t *r)
{
int old = atomic_fetch_add_relaxed(i, &r->refs);
- WARN_ONCE(!old, "refcount_t: addition on 0; use-after-free.\n");
- if (unlikely(old <= 0 || old + i <= 0)) {
- refcount_set(r, REFCOUNT_SATURATED);
- WARN_ONCE(old, "refcount_t: saturated; leaking memory.\n");
- }
+ if (unlikely(!old))
+ refcount_warn_saturate(r, REFCOUNT_ADD_UAF);
+ else if (unlikely(old < 0 || old + i < 0))
+ refcount_warn_saturate(r, REFCOUNT_ADD_OVF);
}
/**
@@ -253,10 +260,8 @@ static inline __must_check bool refcount_sub_and_test(int i, refcount_t *r)
return true;
}
- if (unlikely(old < 0 || old - i < 0)) {
- refcount_set(r, REFCOUNT_SATURATED);
- WARN_ONCE(1, "refcount_t: underflow; use-after-free.\n");
- }
+ if (unlikely(old < 0 || old - i < 0))
+ refcount_warn_saturate(r, REFCOUNT_SUB_UAF);
return false;
}
@@ -291,12 +296,8 @@ static inline __must_check bool refcount_dec_and_test(refcount_t *r)
*/
static inline void refcount_dec(refcount_t *r)
{
- int old = atomic_fetch_sub_release(1, &r->refs);
-
- if (unlikely(old <= 1)) {
- refcount_set(r, REFCOUNT_SATURATED);
- WARN_ONCE(1, "refcount_t: decrement hit 0; leaking memory.\n");
- }
+ if (unlikely(atomic_fetch_sub_release(1, &r->refs) <= 1))
+ refcount_warn_saturate(r, REFCOUNT_DEC_LEAK);
}
#else /* CONFIG_REFCOUNT_FULL */